1. Field of the Invention
The present invention relates to a copier, facsimile apparatus, printer or similar image forming apparatus and more particularly to a cleaning unit configured to reduce the degradation of image quality and noise ascribable to vibration that occurs between a cleaning blade and a photoconductive body or image carrier included in an image forming apparatus for thereby achieving a stable cleaning characteristic.
2. Description of the Background Art
A problem with a cleaning unit included in an image forming apparatus is that stick-slip occurs due to friction acting between a cleaning blade and a photoconductive drum or similar image carrier. Vibration ascribable to the stick-slip constitutes a vibration source causing the image carrier to produce noise or is propagated from the cleaning blade to a unit casing to also produce noise. Because a cleaning unit is essential for removing residual toner left on an image carrier after image transfer, it is necessary to reduce such noise.
Further, if relative vibration between the cleaning blade and the image carrier increases, load acting on the drive of the image carrier varies due to the friction of the cleaning blade. As a result, speed variation is aggravated to bring about banding or similar degradation of image quality. Banding refers to a phenomenon that the density of an output image varies in accordance with the frequency of speed variation, lowering image quality. Such a phenomenon is ascribable to an increase in the speed variation of the image carrier mentioned above.
Moreover, when the cleaning blade vibrates due to resonance, a gap is sometimes formed between the image carrier and the edge of the cleaning blade. If the gap is sized greater than toner particles, then toner particles are allowed to pass through the gap and make cleaning defective.
In order to solve the problems stated above, Japanese Patent Laid-Open Publication No. 10-333385, for example, discloses a color image forming apparatus including driving devices against which an image carrier and an intermediate image transfer body are pressed and to which torque is transmitted from a double shaft, double gear motor via gear trains. This color image forming apparatus is characterized in that a dynamic damper or a flywheel is mounted on the motor shaft in order to control the amplification of vibration ascribable to the resonance of the motor. With this configuration, according to the above document, it is possible to reduce the vibration of the image carrier for thereby protecting a latent image formed on the image carrier from disturbance.
Japanese Patent Laid-Open Publication No. 9-222826 teaches that the inertia masses of inertia members, which are included in a rotation driveline, and the numbers of rotations and the numbers of teeth of gears are so selected as to confine the frequency of eccentricity of a rotation driver implemented by gears and the frequency of speed variation based on the meshing of gears in the attenuation range in the frequency response of a rotation driving device. This is successful to prevent the vibration of an apparatus from being amplified.
The problem with the prior art technologies stated above is that vibration is controlled on the basis of the configuration of a driving device, e.g., a dynamic damper or a flywheel or the numbers of teeth or the rotation speeds of gears. As a result, when the number of structural parts, including the dynamic damper or the flywheel and gears, increases, the number of conditions for controlling vibration increases and make the entire configuration sophisticated and bulky.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 60-023874, 11-184307 and 2003-177583.